Gas-liquid contacting apparatus is used in many industries, such as the natural gas industry, for removing desirable or undesirable constituents from gas mixtures. One common use for gas-liquid contacting apparatus is in removal of water vapor from gas, such as natural gas, by intimately contacting the natural gas with a liquid desiccant. Gas-liquid contacting apparatus also is commonly used in aminetype sour gas treaters, absorption-type hydrocarbon liquid recovery plants, and other processes.
In many larger systems, pumping energy for liquid recirculation is supplied from an outside source, such as an engine or electric motor, but in smaller systems, particularly those located remotely in the field, pumping energy is obtained solely from high pressure gas, before or after treatment, as disclosed in Kimmell U.S. Pat. No. 2,990,910.
In Kimmell U.S. Pat. No. 2,990,910, a pumping method and apparatus is disclosed wherein a pump is powered by a combination of liquid and gas from a gas-liquid contact apparatus, such as an absorber, and the pressure of the gas and liquids supplied to the pump is proportional to the amount of gas supplied to the power side of the pump. In this manner, when more gas pressure is supplied to the absorber, more power is supplied to the pump for recirculation of liquid for contact in the absorber. The fluids used to power a Kimray pump comprises two volumes of liquid plus one volume of gas which pumps back to the absorber two volumes of regenerated absorbent. The one volume of power gas is of doubtful quality for use as fuel and, particularly at system pressures greater than 300 psig, the quantity of power gas greatly exceeds the fuel requirement. In these instances, most of that gas is flared or vented to atmosphere, constituting a substantial waste of gas.
In accordance with the present invention, this gas waste has been entirely eliminated by using substantially only liquid to power the liquid recirculation pump and by controlling the rate of liquid recirculation to the gas-liquid contacting apparatus in a manner not directly responsive to the liquid level within the gas-liquid contact apparatus.